NEET 2019 Zoology Mutation Theory MCQ Question

Explanation

Correct Answer: D) random and directionless

Hugo de Vries, a Dutch botanist, is well-known for his work on mutation theory. He proposed that mutations are sudden, heritable changes in the genetic material of an organism, which can lead to variations in traits. Here’s why the correct answer is "random and directionless":

1. Random Nature of Mutations: Mutations occur due to various factors, such as errors during DNA replication, exposure to radiation, or chemical influences. These events are random; they do not occur in a predetermined manner nor do they target specific traits. As a result, the variations produced by mutations can be beneficial, neutral, or harmful without any guiding direction toward adaptation.

2. Directionless Variations: Since mutations can lead to various changes, they do not inherently direct an organism toward a specific evolutionary outcome. While some mutations might confer advantages in certain environments, they arise without any foresight or planning. Therefore, they are directionless in terms of evolutionary progress.

Why Other Options Are Incorrect

A) small and directional

• This option suggests that mutations are small and lead to specific outcomes. While mutations can be small, they are not inherently directional. They can result in a wide range of effects, from minor changes to significant alterations in phenotype, without a consistent direction toward adaptation.

B) small and directionless

• This option acknowledges that mutations can be directionless, but it incorrectly implies that all mutations are small. Mutations can vary widely in their impact; some can be large-scale (such as chromosomal mutations) and have significant consequences for the organism.

C) random and directional

• This option correctly identifies mutations as random but incorrectly asserts that they are directional. As explained, while some mutations may lead to adaptations that are beneficial in a certain context, the mutations themselves occur randomly and do not aim toward a specific evolutionary goal.

Key Concepts

• Mutation: A change in the DNA sequence of an organism that can lead to variation in traits.
• Randomness in Mutations: Mutations arise from various spontaneous processes and are not influenced by the organism's needs.
• Directionlessness: The outcomes of mutations are not aimed at any particular evolutionary target, which aligns with the concept of natural selection acting on random variations.

In summary, mutations as proposed by Hugo de Vries are best described as random and directionless. This understanding is essential for grasping the fundamental principles of evolutionary biology and the role of genetic variation in natural selection.